Initial implementation of differential fuzzing

[satyamakgec]

What was wrong?

• Needs fuzzing of contracts.

How was it fixed?

It consists of the fuzzing setup for the erc20.fe and erc20.sol and has the rearrangements for the compiler tests as an independent directory to avoid circular dependency and it will also decrease the test execution time as it doesn't require rebuilding the dependencies again.

To-Do

• Need to add fuzzing for ERC20.sol.

• Add support for output gathering to differentiate outputs of the contract.

• Add support for the gas analyzing for the contracts

• OPTIONAL: Update Spec if applicable

• Add entry to the release notes (may forgo for trivial changes)

• Clean up commit history

[codecov-commenter]

Codecov Report

Merging #385 (97f4125) into master (df7c1d6) will decrease coverage by 0.12%.
The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master     #385      +/-   ##
==========================================
- Coverage   86.07%   85.95%   -0.13%     
==========================================
  Files          67       68       +1     
  Lines        4008     4285     +277     
==========================================
+ Hits         3450     3683     +233     
- Misses        558      602      +44     

Impacted Files	Coverage Δ
test-utils/src/lib.rs	84.83% <87.50%> (ø)
compiler/src/lowering/names.rs	66.66% <0.00%> (-6.67%)	⬇️

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[sbillig]

@satyamakgec Could you rebase your changes onto the master branch, and maybe squash some of your fixup commits? It's hard to navigate your changes.

[sbillig]

Whoops, misclicked! This laptop has a touchscreen, and there was some dirt over the 'close' button

[sbillig]

@satyamakgec Trying to run the fuzzer fails with

error[E0433]: failed to resolve: could not find `erc20` in `fe_compiler_fuzz`
 --> fuzz_targets/erc20_target.rs:5:23
  |
5 |     fe_compiler_fuzz::erc20::fuzz_fe_erc20_constructor(data);
  |                       ^^^^^ could not find `erc20` in `fe_compiler_fuzz`

Same results with either cd fuzz && cargo build or cargo +nightly fuzz erc20_target. I'm not sure what's going on here. erc20 is clearly exposed by the lib, but maybe it's a simple issue with the file layout or cargo.toml that I'm not noticing. Ideas? Does this build for you? Should I be doing something else?

[satyamakgec]

ohh sorry @sbillig I should have mention this in the readme. It only works with the feature flag i.e solc-backend so the right command to run it cargo +nightly fuzz run erc20_target --features solc-backend. And yes right now it is a mess up in the commits of the PR, I am going to re-open a clean new PR with these changes so it will be very easy to look over to the changes.

[satyamakgec]

Closing in the favour of #421